Zero waste reverse osmosis system and downstream rinsing

ABSTRACT

A system for regulating a reverse osmosis system to obtain zero wastewater includes a fresh water supply, a reverse osmosis apparatus, a concentrate storage tank and a permeate storage tank, a concentrate solenoid valve and a permeate solenoid valve, a permeate heater, an institutional dishmachine and a control system. The reverse osmosis apparatus filters water from the fresh water supply into a concentrate rinse stream and a permeate rinse stream. The concentrate storage tank and the permeate storage tank are downstream of the reverse osmosis apparatus and receiving the concentrate rinse stream and the permeate rinse stream, respectively. The concentrate solenoid valve and the permeate solenoid valve control the flow of the concentrate rinse stream and the permeate rinse stream, respectively, from their respective storage tank. The permeate heater heats the permeate rinse stream to a predetermined temperature. The institutional dishmachine successively receives the concentrate rinse stream and the permeate rinse stream during a rinse cycle of the institutional dishmachine. The control system is operatively connected to the concentrate solenoid valve and the permeate solenoid valve and control flow of the rinse streams into the institutional dishmachine.

FIELD OF THE INVENTION

The present invention relates generally to the field of reverse osmosissystems used in conjunction with institutional dishmachines. Inparticular, the present invention relates to a system for eliminatingwastewater produced by a reverse osmosis system connected to aninstitutional dishmachine. A method of using the reverse osmosis systemis also provided.

BACKGROUND

During the rinse step of a dishwashing cycle, fresh water is sprayedonto the dishware to rinse food soils and detergent from the surface ofthe dishware. When the fresh water is relatively low in dissolved solids(i.e., minerals in the water), the dishware appears substantiallyfilm-free and spot-free after it dries. However, when the fresh watercontains high levels of dissolved solids, the dried dishware can have asignificant amount of visible film and spots due to the minerals in thewater. The solids remain on the dishware after the water evaporates,leaving behind rather unsightly film and spots, especially on glassware,flatware, and dark-colored dishware items.

Reverse osmosis is an effective mechanism for removing dissolved solidsfrom water in areas that have high levels of dissolved solids in thewater. However, reverse osmosis systems by nature waste water because tomaintain the membrane of the system in functional working condition, themembrane surface is periodically flushed with water, which issubsequently discarded. The concentrate (wastewater) is passed at highflow rates across the membrane surface to remove solids from the surfaceto prevent the membrane from getting plugged and fouled. If 100% of thewater were forced through the membrane, the membrane life would bereduced and the flow of water (production of permeate) would be severelyreduced. Therefore, the most efficient way to operate a reverse osmosissystem is to waste a certain amount of water.

There are various ways to reduce the amount of wastewater from a reverseosmosis system, including recycling the concentrate water back to thereverse osmosis feed and using multiple membranes in series. However,for practical purposes, the reverse osmosis system will still createsome wastewater. In the current state of the art for a commercialreverse osmosis system, a ratio of about 50% permeate to about 50%concentrate has been found to provide an effective balance for allowinga reverse osmosis system to operate in a wide variety of waterconditions while minimizing the amount of equipment involved in theoverall system.

SUMMARY

In an embodiment, the present invention relates to a method ofeliminating wastewater in a reverse osmosis apparatus connected to aninstitutional dishmachine. The method includes introducing a waterstream into the reverse osmosis apparatus to split the water stream intoa permeate rinse stream and a concentrate rinse stream, rinsing dishwarein a rinse cycle of the institutional dishmachine with the concentraterinse stream and subsequently rinsing the dishware in the rinse cycle ofthe institutional dishmachine with the permeate rinse stream. The ratioof the concentrate rinse stream to the permeate rinse stream is about3:2 or less. The permeate rinse stream has a total dissolved solidsconcentration of about 200 parts per million or less.

In another embodiment, the present invention relates to a reverseosmosis system connectable to an institutional dishmachine. The reverseosmosis system includes a fresh water supply, a reverse osmosisapparatus for splitting water from the fresh water supply into aconcentrate stream and a permeate stream; a concentrate storage tank anda permeate storage tank downstream of the reverse osmosis apparatus forreceiving the concentrate stream and the permeate stream, respectively;a heater for heating the permeate stream to a predetermined temperature;and a control system for selectively controlling flow of the concentratestream and flow of the permeate stream such that the reverse osmosissystem produces zero wastewater.

In another embodiment, the present invention relates to a system forregulating a reverse osmosis apparatus to obtain zero wastewater. Thesystem includes a fresh water supply, a reverse osmosis apparatus, aconcentrate storage tank and a permeate storage tank, a concentratesolenoid valve and a permeate solenoid valve, a permeate heater, aninstitutional dishmachine and a control system. The reverse osmosisapparatus filters water from the fresh water supply into a concentraterinse stream and a permeate rinse stream. The concentrate storage tankand the permeate storage tank are located downstream of the reverseosmosis apparatus and receive the concentrate rinse stream and thepermeate rinse stream, respectively. The concentrate solenoid valve andthe permeate solenoid valve control the flow of the concentrate rinsestream and the permeate rinse stream, respectively, from its respectivestorage tank. The heater heats the permeate rinse stream to apredetermined temperature. The institutional dishmachine successivelyreceives the concentrate rinse stream and the permeate rinse streamduring a single rinse cycle of the institutional dishmachine. Thecontrol system is operatively connected to the concentrate solenoidvalve and the permeate solenoid valve and controls flow of the rinsestreams into the institutional dishmachine.

BRIEF DESCRIPTION OF THE FIGURE

The FIGURE is a schematic view of a zero waste dishwashing system,according to one embodiment of the present invention.

While the invention is amenable to various modifications and alternativeforms, specific embodiments have been shown by way of example in thedrawings and are described in detail below. The intention, however, isnot to limit the invention to the particular embodiments described. Onthe contrary, the invention is intended to cover all modifications,equivalents, and alternatives falling within the scope of the inventionas defined by the appended claims.

DETAILED DESCRIPTION

The sole FIGURE shows a schematic view of a zero waste dishwashingsystem 10 including an institutional dishmachine 12 with an integratedreverse osmosis system 14. The dishwashing system 10 reduces and/oreliminates wastewater associated with conventional reverse osmosissystems by splitting a fresh water stream into two rinse streams, aconcentrate rinse stream and a permeate rinse stream. The concentraterinse stream and the permeate rinse stream are then used to rinsedishware during a single, discrete rinse cycle of the institutionaldishmachine. Thus, rather than discarding the concentrate, orwastewater, created from the reverse osmosis system 14, the concentrateis used in a first part of the rinse cycle and the permeate, or purifiedwater, is used in a second part of the rinse cycle. The dishwashingsystem 10 of the present invention achieves substantially the samewarewashing results as an institutional dishmachine 12 using a reverseosmosis system that conducts the entire rinse cycle using only permeate.Because the reverse osmosis system 14 utilizes wastewater at the samerate at which it is produced, the reverse osmosis system 14 isself-regulating and can be operated with zero wastewater, regardless ofhow often the institutional dishmachine 12 operates during a particularhour or day. In addition, the reverse osmosis system 12 also reducesenergy consumption of the dishwashing system 10 during the rinse cycleof the institutional dishmachine 12.

The institutional dishmachine 12 may be any rinsing apparatus orconventional institutional dishmachine used to wash dishware incommercial settings, for example, a door-type dishmachine, a glasswashing dishmachine or an undercounter dishmachine. An entire run forthe institutional dishmachine 12 typically lasts between about 60seconds and about 90 seconds and is generally broken into a single washcycle and a single rinse cycle. Typically, the wash cycle lasts betweenabout 30 seconds and about 60 seconds and the rinse cycle lasts betweenabout 8 seconds and about 30 seconds. Optionally, there is a dwell orpause time after each of the wash and rinse cycles lasting between about5 seconds to about 10 seconds.

During the wash cycle, water is recirculated from a wash tank over thedishware using a pump located in the institutional dishmachine 12. Thewater typically includes chemicals for cleaning the dishware. The flowrate of the (pumped) recirculated wash water is typically between about60 gallons per minute and about 200 gallons per minute.

After the dishware has been cleaned during the wash cycle, any foodparticles and chemicals are rinsed from the surface of the dishwareduring the rinse cycle. While the water used during the wash cycle isrecirculated water, the water used during the rinse cycle is fresh waterand is first passed through the reverse osmosis system 14 before beingsent to the institutional dishmachine 12. In one embodiment, water isintroduced into the institutional dishmachine 12 during the rinse cycleat a flow rate of between about 4 gallons per minute and about 8 gallonsper minute.

The reverse osmosis system 14 is automatically balanced in that thereverse osmosis system 14 uses substantially exactly the amount of freshwater that is introduced into the dishwashing system 10. Even though thereverse osmosis system 14 is integrated with the institutionaldishmachine 12, the dishwashing system 10 uses the same amount of waterto rinse the dishware in the institutional dishmachine 12 as if noreverse osmosis system 14 were present. The footprint of the reverseosmosis system 14 can therefore be downsized from conventional reverseosmosis systems by about one half because it only has to supply half theamount of permeate water in each rinse cycle. The concentrate water,normally discarded as wastewater, is used for the other half of therinse cycle, thus using only half of the permeate water and resulting ina system that is approximately half as large as a conventional reverseosmosis system. Equipment used in or in conjunction with the reverseosmosis system 14, such as a pre-filter, reverse osmosis membranes,water storage tanks, and heaters can all be downsized by about 50%,resulting in a much smaller overall system.

In addition, as the dishwashing system 10 uses the same amount of waterand the same cycle times as an institutional dishmachine that does notinclude a reverse osmosis system, the institutional dishmachine 12 doesnot need to be changed to be used in conjunction with the reverseosmosis system 14. The reverse osmosis system 14 can thus be integratedwith conventional institutional dishmachines with very little to noalterations to the institutional dishmachine 12.

The reverse osmosis system 14 is connected to the institutionaldishmachine 12 and includes a fresh water supply 16, an inlet solenoidvalve 18, a pre-filter 20, a reverse osmosis apparatus 22, a concentratesupply line 24, a concentrate check valve 26, a concentrate storage tank28, a concentrate solenoid valve 30, a concentrate heater 32, a permeatesupply line 34, a permeate check valve 36, a permeate storage tank 38, apermeate solenoid valve 40, a permeate heater 42, a pressure switch 44,a control system 46 and a circulation system 48 for transporting waterthrough the reverse osmosis system 14. Generally, water flows from thefresh water supply 16 and through the pre-filter 20 before reaching thereverse osmosis apparatus 22. The reverse osmosis apparatus 22 separatesthe water into a permeate rinse stream and a concentrate rinse stream.The water from each of the rinse streams is collected in its respectivestorage tank 28, 38 until the institutional dishmachine 12 calls for thewater during the rinse cycle. Each of the concentrate solenoid valve 30and the permeate solenoid valve 40 receives a signal in successive orderto open and allow water to flow from the concentrate and permeatestorage tanks 28, 38 to the institutional dishmachine 12 to rinse thedishware in the institutional dishmachine 12.

The inlet solenoid valve 18 controls the amount of water that enters thereverse osmosis system 14 from the fresh water supply 16. The water inthe fresh water supply 16 is sourced by the building that thedishwashing system 10 is located in, and can be, for example, wellwater. The water from the fresh water supply 16 can be supplied atbuilding line pressure, or the pressure can be boosted by a highpressure pump to increase the production rate and the water efficiencylevel. Depending on the location, the total dissolved solids (TDS) ofthe water will vary. The term “dissolved solids” refers to the presenceof various minerals, metals, and salts in the water. In general,high-solids water refers to water having a total dissolved solidsconcentration in excess of about 300 ppm. However, high-solids wateroften has a TDS concentration in excess of about 500 ppm, and even inexcess of about 800 ppm. Although all locations have at least somesolids dissolved in the water, the TDS tends to vary from one locationto another.

The pre-filter 20 is located downstream from the fresh water supply 16and filters out sediment and removes chlorine from the water flowingfrom the fresh water supply 16 before the water enters the reverseosmosis apparatus 22. Both sediments and chlorine are harmful to themembrane in the reverse osmosis apparatus 22 and can reduce the life ofthe membrane. Any pre-filter that is capable of filtering out sedimentand chorine from water can be used with the reverse osmosis system 14.Although FIG. 1 depicts only one pre-filter 20, the reverse osmosissystem 14 may include any number of pre-filters without departing fromthe intended scope of the present invention. For example, if the waterfrom the fresh water supply 16 has a high concentration of sedimentand/or chorine, a number of pre-filters may be positioned in seriesupstream of the reverse osmosis apparatus 22 to ensure that theconcentration of the sediment and/or chorine entering the reverseosmosis apparatus 22 is not at a detrimental level to the membrane inthe reverse osmosis apparatus 22.

After the water has been passed through the pre-filter 20, the waterenters the reverse osmosis apparatus 22. The reverse osmosis apparatus22 splits the water from the fresh water supply 16 into a concentraterinse stream containing concentrate and a permeate rinse streamcontaining permeate. The concentrate and permeate rinse streams aredirected through the concentrate supply line 24 and the permeate supplyline 34 to the concentrate storage tank 28 and the permeate storage tank38, respectively. As the water flows through the reverse osmosisapparatus 22, the original TDS concentration of the fresh water from thefresh water supply 16 is filtered to create the concentrate rinse streamand the permeate rinse stream such that the TDS concentration of theconcentrate rinse stream is substantially higher than the original TDSconcentration and the TDS concentration of the permeate rinse stream issubstantially lower than the original TDS concentration. For example,after passing through the reverse osmosis apparatus 22, a fresh watersupply 16 having a TDS concentration of about 450 ppm may be outputtedas concentrate rinse stream having a TDS concentration of between about600 ppm and about 1000 ppm and a permeate rinse stream having a TDSconcentration of between about 50 ppm and 200 ppm. As the TDSconcentration of the permeate rinse stream decreases, the TDSconcentration of the concentrate rinse stream increases. The reverseosmosis apparatus 22 is particularly set such that the permeate rinsestream effectively rinses dishware without leaving spots, films orstreaks. In some embodiments, the reverse osmosis apparatus 22 is setsuch that the permeate rinse stream has a TDS concentration of about 200ppm or less, about 150 ppm or less, about 100 ppm or less, or about 50ppm or less.

The reverse osmosis apparatus 22 is a membrane filter and may includemore than one membrane. The membranes may be hollow fiber or spiralwound. Examples of suitable materials used to produce the membranesinclude cellulose tri-acetate (CTA), cellulose acetate (CA), polyamideand thin film composite (TFC). The membranes can also be consideredstandard pressure (high pressure) or low energy (low pressure). Examplesof commercially available reverse osmosis membranes include spiral-woundTFC membranes, model number XLE-4021 (low energy) and TW30-4021 (highenergy), available from Filmtec, Midland Mich. While the dishwashingsystem 10 is discussed as including a reverse osmosis apparatus 22 tofilter an inlet stream into a concentrate rinse stream and a permeaterinse stream, any filtration apparatus that results in a concentraterinse stream and a permeate rinse stream may be used without departingfrom the intended scope of the present invention. For example, othermembrane filtration apparatuses that can be used in conjunction with thedishwashing system 10 include nanofiltration apparatuses,ultrafiltration apparatuses and microfiltration apparatuses. An exampleof a commercially available nanofiltration membrane includes modelnumber M-N4021A9, available from AMI, Vista, Calif. The particular typeof apparatus that is used in the dishwashing system 10 will depend onthe degree of filtration needed for the particular application and theparticular source water quality.

The concentrate and permeate check valves 26, 36 are located upstream ofthe storage tanks 28, 38 and prevent water from flowing backwards fromthe concentrate and permeate storage tanks 28, 38, respectively, to thereverse osmosis apparatus 22.

The concentrate and permeate storage tanks 28, 38 store the concentrateand permeate, respectively, until needed by the institutionaldishmachine 12. The storage tanks 28, 38 can be pressurized tanks oratmospheric tanks. Alternatively, the concentrate and permeate storagetanks 28, 38 may not be needed if the production rate of the reverseosmosis apparatus 22 is high enough to deliver the flow rate requiredfor the particular application. However, a reverse osmosis system 14without concentrate and permeate storage tanks 28, 38, or with onlysmall concentrate and permeate storage tanks 28, 38, would need to bephysically larger to produce water at a faster, on demand rate.

When the permeate storage tank 38 is full, the pressure switch 44connected to the permeate storage tank 38 sends a signal to the inletsolenoid valve 18 to close in order to stop the supply of water from thefresh water supply 16 into the reverse osmosis system 14. With the inletsolenoid valve 18 closed, the fresh water supply 16 no longer deliverswater through the reverse osmosis apparatus 22 to either the concentratestorage tank 28 or the permeate storage tank 38. While the pressureswitch 44 is depicted in the FIGURE as being connected to the permeatestorage tank 38, alternatively, the pressure switch 44 may be located onthe concentrate storage tank 28, or on both storage tanks 28, 38 withoutdeparting from the intended scope of the present invention. If theconcentrate and permeate storage tanks 28, 38 are atmospheric tanks, thepressure switch 44 is replaced by a float switch, with the same generalpurpose of shutting off the reverse osmosis system 14 when the storagetanks 28, 38 are full or reach a pre-set pressure or height.

The concentrate and permeate heaters 32, 42 are located downstream fromtheir respective storage tanks 28, 38 and vary in their temperaturesettings depending on the type of sanitization that the institutionaldishmachine 12 is set up for. For example, the heater temperatures maybe set to about 120° F. for chemical sanitizing or about 180° F. for hotwater sanitizing. For a high temperature sanitizing machine, the rinsewater typically needs to be heated to about 180° Fahrenheit (° F.) tomeet regulatory agency sanitization standards. By splitting thefreshwater stream into a separate concentrate rinse stream and permeaterinse stream, the concentrate rinse stream may be heated to a lowertemperature while the permeate rinse stream is heated to about 180° F.and still comply with regulatory agency sanitization standards. In oneembodiment, the concentrate stream is heated to about 165° F. Becausethe entire volume of rinse water is not heated to the higher 180° F.temperature, there is an overall reduction in energy used during therinse cycle. Although the sole FIGURE depicts the reverse osmosis system14 as including a concentrate heater 32 and a permeate heater 42, theheaters 32, 42 are optional depending on the sanitizing method used inthe institutional dishmachine 12. For example, in some chemicalsanitizing institutional dishmachines, the heaters 32, 42 are notnecessary because the chemicals typically require a cold watersanitizing rinse. In some embodiments, the reverse osmosis system 14 mayinclude the permeate heater 42 but not the concentrate heater 32 if thepermeate heater 42 can heat the permeate to a temperature sufficient tosanitize the dishware. The prime energy savings comes from the fact thatonly half of the water used during the rinse cycle needs to be heated.Thus, an energy savings of up to about 50% can be obtained on thelargest energy consuming component of the dishwashing system 10. Theconcentrate heater 32 may also not be needed if the concentrate canharness heat from another source such that it does not need to bedirectly heated. In one embodiment, the concentrate heater 32 harnessesthe waste heat from the permeate heater 42, thus saving energy andeliminating the need for a concentrate heater.

The control system 46 is operatively connected to the institutionaldishmachine 12 and the concentrate and permeate solenoid valves 30, 40to selectively control the flow of concentrate from the concentratestorage tank 28 and the flow of permeate from the permeate storage tank38 to the institutional dishmachine 12.

When a wash and rinse run of the institutional dishmachine 12 reachesthe rinse cycle, the institutional dishmachine 12 sends a signal to thecontrol system 46. In one embodiment, the control system 46 sends a 10second rinse signal that powers the concentrate and permeate solenoidvalves 30, 40 to divide the rinse cycle into two portions. When firstenergized by the rinse signal from the institutional dishmachine 12, thecontrol system 46 sends a power signal to the concentrate solenoid valve30 to open the concentrate solenoid valve 30, allowing the concentrateto flow into the institutional dishmachine 12 to rinse the dishware inthe institutional dishmachine 12 during the first portion of the rinsecycle. The concentrate solenoid valve 30 remains open for a pre-setperiod time, for example between 0 seconds and 9 seconds. In oneembodiment, the concentrate solenoid valve 30 is open for about 5seconds.

After the signal to the concentrate solenoid valve 30 is completed, thecontrol system 46 then sends a power signal to open the permeatesolenoid valve 40, allowing the permeate to flow into the institutionaldishmachine 12 to rinse the dishware in the institutional dishmachine 12during the second portion of the rinse cycle. The signal to the permeatesolenoid valve 40 occurs immediately following the signal to theconcentrate solenoid valve 30 and also lasts for a pre-set period oftime, for example between 1 seconds and 10 seconds, depending on thelength of the signal to the concentrate solenoid valve 30. Generally,the concentrate solenoid valve 30 is open for C seconds and the permeatesolenoid valve 40 is open for (R−C) seconds, where C is the length ofthe signal to the concentrate solenoid valve 30 and R is the maximumlength of the rinse cycle. For example, if R is 10 seconds and theconcentrate solenoid valve 30 is open for 5 seconds (C), then thepermeate solenoid valve 40 is open for 5 seconds. In one embodiment, theconcentrate solenoid valve 30 and the permeate solenoid valve 40 areopen at a time ratio of at least about 3:2 and particularly at a timeratio of at least about 1:1. In one embodiment, the control system 46 isa timer.

Generally, two factors control the ability of the concentrate rinsestream and the permeate rinse stream to effectively rinse dishwarelocated in the institutional dishmachine 12, 1) the TDS concentration ofthe permeate rinse stream and 2) the amount of time the concentrate isused to rinse the dishware during the rinse cycle relative to the amountof time the permeate is used to rinse the dishware during the rinsecycle, or the time ratio of concentrate to permeate. As the TDSconcentration of the permeate rinse stream decreases, the time ratio ofconcentrate to permeate can increase while still achieving the samecleaning results. For example, a rinse cycle using a permeate rinsestream having a TDS concentration of about 50 ppm, at a concentrate topermeate time ratio of about of about 3:2, will clean dishwaresubstantially as effectively as a rinse cycle using a permeate rinsestream having a TDS concentration of about 100 ppm, at a concentrate topermeate time ratio of about 2:3. Thus, the TDS concentration of thepermeate rinse stream and the time ratio of concentrate to permeate arerelated such that the time ratio of concentrate to permeate may bevaried depending on the TDS concentration of the permeate rinse stream.

Although the rinse cycle is discussed as being divided into two partsaccording to a time ratio to introduce the concentrate rinse stream andthe permeate rinse stream into the institutional dishmachine 12, therinse cycle may be split according to a number of variables. Forexample, the rinse cycle may be discussed as being split according to apercentage of the total volume of water used in the rinse cycle of theinstitutional dishmachine 12. In one embodiment, for an institutionaldishmachine using a total of 1 gallon of water during the rinse cycle,the concentrate stream may constitute about 60% or less of the totalrinse cycle. This would substantially be the equivalent of a concentraterinse stream to permeate rinse stream time ratio of about 3:2.

After the signal to the permeate solenoid valve 42 terminates, the rinsesignal from the institutional dishmachine 12 is terminated, ending therinse cycle and completing the wash and rinse run of the institutionaldishmachine 12. Although the control system 46 is described ascontrolling the amount of time the concentrate and permeate solenoidvalves 30, 40 are open, the control system 46 can optionally measureand/or control a number of variables, for example, the TDS concentrationof the concentrate rinse stream and the permeate rinse stream and theflow rate of the concentrate rinse stream and the permeate rinse stream.

EXAMPLES

The present invention is more particularly described in the followingexamples that are intended as illustrations only, since numerousmodifications and variations within the scope of the present inventionwill be apparent to those skilled in the art. Unless otherwise noted,all parts, percentages, and ratios reported in the following examplesare on a weight basis, and all reagents used in the examples wereobtained, or are available, from the chemical suppliers described below,or may be synthesized by conventional techniques.

Test Method

An institutional dishmachine was prepared for use under normal operatingprocedures. The institutional dishmachine was set to automaticallydispense and maintain a normal amount of detergent and rinse additive.The institutional dishmachine was allowed to reach normal operatingtemperature. A first water storage tank was filled with concentratewater having a TDS concentration of about 750 ppm and a second waterstorage tank was filled with permeate water having a TDS concentrationof about 50 ppm, about 100 ppm, about 150 ppm or about 200 ppm,depending on the test condition.

For each test condition, a set of 4 glasses was placed into theinstitutional dishmachine. A complete wash and rinse run was conductedwith the institutional dishmachine running automatically and the timersequenced with the appropriate rinse water type and time. As soon as theentire dishwashing run was complete, the glassware was removed andallowed to air dry under ambient conditions.

Once dry, the glasses were rated using three ratings of spot, film andstreak. A focused light source was used to exaggerate the spots, filmand streaks so that subtle differences between conditions could bedetected. Each glass was rated on a scale of 1 to 5 with respect to eachof these properties. A rating of 1 indicated no presence of the propertyand a rating of 5 indicated a heavy presence of the property. Theratings of all four glasses for each set were averaged and recorded.

The average spot, film and streak ratings were summed for an overallglassware appearance rating. The range of possible glassware ratings wasthus from 3 to 15, with 3 being perfect and 15 being poor or heavy. Anoverall glassware rating of 5.0 or less was considered excellent. Spots,films and streaks are hard to see with the naked eye when their combinedtotal is less than 5.0.

EXAMPLES

A series of cycles were run to determine a range of concentrate topermeate time ratios and a range of permeate rinse TDS concentrations ina rinse cycle that would result in glassware having acceptable spot,film and streak ratings. To determine the ranges, the concentrate topermeate time ratio and the permeate rinse TDS concentration werevaried. The source of the concentrate rinse was wastewater from areverse osmosis system.

Fresh rinse water entered the reverse osmosis system with a TDSconcentration of about 450 ppm and was split into a concentrate rinsestream and a permeate rinse stream. The concentrate rinse stream and thepermeate rinse stream were supplied during the rinse cycle of theinstitutional dishmachine for predetermined amounts of time. Theconcentrate rinse stream was first supplied into the institutionaldishmachine for a predetermined amount of time during the rinse cycle,with the permeate rinse stream being supplied for the remainder of therinse cycle. The entire rinse cycle time totaled 10 seconds. Theconcentrate to permeate time ratio and the TDS concentration of thepermeate rinse were varied for each rinse cycle run. After the glasseswere rinsed and allowed to dry, the spot, film and streak ratings werenoted. Because the ratings are in part subjective, the runs wererandomized to prevent bias.

Table 1 provides the concentrate rinse time and TDS concentration of thepermeate of each run and the resulting spot, film and streak ratings ofthe dishware.

TABLE 1 Con- Permeate centrate Rinse Rinse TDS Spot Film Streak SummedRun Time (sec) (ppm) Rating Rating Rating Rating Run 1 0 100 1 1.5 1.5 4Run 2 6 150 1 5 1.75 7.75 Run 3 2 50 1 1.5 1 3.5 Run 4 4 150 1 2.25 25.25 Run 5 6 200 1.1 4 1.25 6.35 Run 6 2 100 1 1 1.25 3.25 Run 7 2 200 13 1.25 5.25 Run 8 4 50 1 1.5 1 3.5 Run 9 6 100 1 3 2 6 Run 10 0 200 12.75 1.25 5 Run 11 0 50 1 1.5 1.5 4 Run 12 0 150 2 2.75 1.5 6.25 Run 136 50 1 4.5 1.25 3.75 Run 14 2 150 1 2.25 1.5 4.75 Run 15 4 200 1 3 1.755.75 Run 16 4 100 1 1.75 1.5 4.25 Run 17 2 100 1 1.75 1.25 4 Run 18 6150 1 3.5 1.75 6.25 Run 19 6 50 1 2.25 1.5 4.75 Run 20 4 200 1 3.75 1.56.25 Run 21 6 100 1 1.75 1.25 4 Run 22 6 200 1 4 1.75 6.75 Run 23 2 1501 1.75 1.25 4 Run 24 2 200 1 3.5 1.75 6.25 Run 25 4 150 1 2.25 1.75 5Run 26 0 50 1 1 1 3 Run 27 0 150 1 1.75 1.5 4.25 Run 28 0 100 1 1.25 13.25 Run 29 4 50 1 1.35 1 3.35 Run 30 4 100 1 2 1.5 4.5 Run 31 2 50 11.25 1 3.25 Run 32 0 200 1 2.25 1.5 4.75

As can be seen in Table 1, a permeate rinse stream having a TDSconcentration of about 100 or less resulted in substantially spot-free,film-free and streak-free glasses regardless of the concentrate rinsetime. Based on these results, a more narrow range of runs (“second setof runs”) were performed using the same method described above. Thesecond set of runs had a total rinse cycle time of 10 seconds and usedpermeate rinse streams having a TDS concentration of about 50 ppm andabout 100 ppm. Table 2 below provides the overall ratings for thevarious concentrate to permeate time ratios and TDS concentrations ofthe permeate rinse stream.

TABLE 2 Concentrate Permeate Overall Glass Rating Rinse Stream RinseStream 50 ppm 100 ppm Time (sec) Time (sec) permeate permeate 0 10 3.53.62 2 8 3.38 3.62 4 6 3.42 4.38 6 4 4.25 5.0 750 ppm concentrate 10 010

As illustrated in Table 2, glasses treated for the entire 10 secondrinse cycle with a permeate rinse stream having a TDS concentration ofabout 50 ppm to about 100 ppm resulted in glasses with substantially nospots, films or streaks. The data in Table 2 also shows that slightlybetter results were obtained by using permeate rinse streams with alower TDS concentration. That is, the overall appearance of theglassware was slightly better when the permeate rinse stream containedonly about 50 ppm TDS compared to a permeate rinse stream that containedabout 100 ppm TDS.

This was true even when the concentrate to permeate time ratio wasslightly higher than the conventionally effective 1:1 time ratio. It wassurprisingly discovered that excellent results could be achieved usingup to about 6 seconds of concentrate followed by only about 4 seconds ofpermeate. While the overall glass ratings indicated that the glasses hadsubstantially no spots, films or streaks with a 0 or 2 secondconcentrate rinse, followed by a 10 second or 8 second permeate rinse,respectively, the overall glass rating was still excellent with a 6second concentrate rinse, followed by a 4 second permeate rinse. It wasunexpected that the high-quality permeate rinse stream compensated forthe long duration of the lower-quality concentrate rinse stream.

By comparison, when the entire 10 seconds of rinse cycle was conductedusing only concentrate (about 750 ppm TDS), the resulting glasses had arating of 10, or very poor.

The present invention is a zero waste reverse osmosis system that splitsa water source that may have poor rinsing properties into a concentratedrinse stream and a purified rinse stream. By passing the water sourcethrough a reverse osmosis apparatus to concentrate the minerals in thewater source into a first part of a rinse cycle and following with apurified water rinse, dishware washed with the water source aresubstantially spot-free, streak-free and film-free. This is true eventhough the properties of the original water source did not change.Because the wastewater produced by the reverse osmosis apparatus is alsoused to rinse the dishware, no water is wasted by the overall reverseosmosis system.

It should be noted that, as used in this specification and the appendedclaims, the singular forms “a,” “an,” and “the” include plural referentsunless the content clearly dictates otherwise. Thus, for example,reference to a composition containing “a compound” includes a mixture oftwo or more compounds. It should also be noted that the term “or” isgenerally employed in its sense including “and/or” unless the contentclearly dictates otherwise.

All publications and patent applications in this specification areindicative of the level of ordinary skill in the art to which thisinvention pertains. All publications and patent applications are hereinincorporated by reference to the same extent as if each individualpublication or patent application was specifically and individuallyindicated by reference.

The invention has been described with reference to various specific andpreferred embodiments and techniques. However, it should be understoodthat many variations and modifications may be made while remainingwithin the spirit and scope of the invention.

1. A method of eliminating wastewater in a reverse osmosis apparatusthat supplies water to an institutional dishmachine, the methodcomprising: a) introducing a water stream into the reverse osmosisapparatus to split the water stream into a permeate rinse stream and aconcentrate rinse stream; b) rinsing dishware during a rinse cycle ofthe institutional dishmachine with the concentrate rinse stream; and c)rinsing the dishware during the rinse cycle of the institutionaldishmachine with the permeate rinse stream after rinsing the dishwarewith the concentrate rinse stream; d) wherein a ratio of the concentraterinse stream to the permeate rinse stream is about 3:2 or less; and e)wherein the permeate rinse stream has a total dissolved solidsconcentration of about 200 parts per million or less.
 2. The method ofclaim 1, wherein the ratio of the concentrate rinse stream to thepermeate rinse stream is about 1:1 or less.
 3. The method of claim 1,wherein the ratio is one of a time ratio and a volume ratio.
 4. Themethod of claim 1, wherein the rinse cycle is completed in less thanabout 20 seconds.
 5. The method of claim 1, wherein the permeate rinsestream has a total dissolved solids concentration of about 100 parts permillion or less.
 6. The method of claim 5, wherein the permeate rinsestream has a total dissolved solids concentration of about 50 parts permillion or less.
 7. The method of claim 1, further comprising heatingthe permeate rinse stream to at least about 180 degrees Fahrenheit.
 8. Areverse osmosis system connectable to an institutional dishmachine, thesystem comprising: a) a fresh water supply; b) a reverse osmosisapparatus for splitting water from the fresh water supply into aconcentrate stream and a permeate stream; c) a concentrate storage tankand a permeate storage tank downstream of the reverse osmosis apparatusfor receiving the concentrate stream and the permeate stream,respectively; d) a heater for heating the permeate stream to apredetermined temperature; and e) a control system for selectivelycontrolling flow of the concentrate stream and flow of the permeatestream such that the reverse osmosis system produces zero wastewater. 9.The reverse osmosis system of claim 8, wherein the reverse osmosisapparatus splits the water from the fresh water supply into theconcentrate stream and the permeate stream at a ratio of about 3:2 orless.
 10. The reverse osmosis system of claim 8, wherein the reverseosmosis apparatus splits the water from the fresh water supply such thatthe permeate stream has a total dissolved solids concentration of about200 parts per million or less.
 11. The reverse osmosis system of claim10, wherein the reverse osmosis apparatus splits the water from thefresh water supply such that the permeate stream has a total dissolvedsolids concentration of about 100 parts per million or less.
 12. Thereverse osmosis system of claim 8, wherein the control system comprisesa timer.
 13. The reverse osmosis system of claim 8, further comprising apressure switch connected to at least one of the concentrate storagetank and the permeate storage tank.
 14. The reverse osmosis system ofclaim 8, wherein the heater heats the permeate stream to at least about180 degrees Fahrenheit.
 15. The reverse osmosis system of claim 8,wherein the heater heats the concentrate stream to at least about 165degrees Fahrenheit.
 16. A system for regulating a reverse osmosis systemto obtain zero wastewater, the system comprising: a) a fresh watersupply; b) a reverse osmosis apparatus for filtering water from thefresh water supply into a concentrate rinse stream and a permeate rinsestream; c) a concentrate storage tank located downstream of the reverseosmosis apparatus for receiving the concentrate rinse stream; d) aconcentrate solenoid valve for controlling flow of the concentrate rinsestream from the concentrate storage tank; e) a permeate storage tanklocated downstream of the reverse osmosis apparatus for receiving thepermeate rinse stream; f) a permeate solenoid valve for controlling flowof the permeate rinse stream from the permeate storage tank; g) a heaterfor heating the permeate rinse stream to a predetermined temperature; h)an institutional dishmachine for successively receiving the concentraterinse stream and the permeate rinse stream during a rinse cycle of theinstitutional dishmachine; and i) a control system operatively connectedto the concentrate solenoid valve and the permeate solenoid valve forcontrolling flow of the concentrate rinse stream and the permeate rinsestream, respectively, into the institutional dishmachine.
 17. The systemof claim 16, wherein the concentrate rinse stream constitutes at leastabout 60% by volume of the rinse cycle.
 18. The system of claim 16,wherein the concentrate rinse stream and the permeate rinse stream flowinto the institutional dishmachine at a time ratio of about 3:2 or less.19. The system of claim 16, wherein the permeate rinse stream has atotal dissolved solids concentration of less than about 100 parts permillion.
 20. The system of claim 16, wherein the control systemcomprises a timer.
 21. The system of claim 16, further comprising apressure switch connected to at least one of the concentrate storagetank and the permeate storage tank.
 22. The system of claim 16, whereinthe rinse cycle lasts less than about 20 seconds.